Fatigue Life Monitoring System for Aircraft to Flexibilize Operations and Maintenance Planning

Abstract

The damage tolerance analysis, which uses the force structural management plan, is usually employed in airplane fatigue life prediction. This plan, based on a mission “mix” defined at the airplane structure design phase, induces the squadrons to follow this mix and interferes in the fleet’s usage efficiency. Deviations in the mission mix have impacts on inspection intervals and maintenance costs. In this paper, a fatigue life monitoring system is proposed. It is able to incorporate each mission, individually, in a specific aircraft’s fatigue life analysis, adjusting the maintenance plan into a more realistic usage profile, based on the individual aircraft tracking methodology. This monitoring system is implemented in a computer software and it is applied to F-5E fighter aircraft of the Brazilian Air Force. In addition, experimental fatigue tests that simulate critical locations of this aircraft are compared with the proposed monitoring system, which shows ability to predict, in conservative and approximate ways, the crack length after each flight, disregarding the predefined mission mix. This makes the flexibilization of the operations possible without jeopardizing the inspection and maintenance planning.